Lawn-mowers with horizontally rotating knives

ABSTRACT

A lawn-mower with horizontally rotating knives has an ejection aperture formed in a casing enclosing the rotary knives. Screening means are arranged in the ejection aperture to prevent accidents. The knives of the lawn-mower function in the manner of fan blades so as to cause the uncut grass to stand on end and to lift the cut-off grass blades to a level above the path of the knives. The knife unit also includes another fan device which produces a flow of air directed towards the ejection aperture and carrying the cut-off grass outwards through this aperture. Further, screening means are disposed above the ejection aperture at a level with the path of motion of the knives, and the ejection of the grass has to take place through a portion of the aperture that lies above the screened portion of the ejection aperture.

[451 Dec. 12,1972

[541 LAWN-MOWERS WITH HORIZONTALLY ROTATING KNIVES [72] Inventor StigGunnar I-Ijelmquist, Box 6, S- 57301 Tranas, 1, Sweden 22 Filed:0.19,1971

[21] Appl.No.: 190,673

[30] Foreign Application Priority Data Oct. 21, 1970 Sweden ..14l6 0/70[52] U.S. Cl. ..56/320.2 [51] Int. Cl. ..A01d 55/18 [58] Field ofSearch....56/320.2, 295, 255, 17.5, 17.4

[56] References Cited UNITED STATES PATENTS 2,071,872 2/1937 Cockbumm...56/13.4

2,675,661 4/1954 Titzer ..56/17.2 2,708,334 5/1955 Coners ..56/320.22,719,396 10/1955 Morris et a1. ..56/l2.2 2,864,226 12/1958 Bright.......56/l3.4 3,540,198 11/1970 Heth et al.... ..,.56/295 3,646,740 3/1972Grimesm; ..56/320.2 3 ,648,445 3/1972 Efflandt ..56/320.2

FOREIGN PATENTS OR APPLICATIONS 223,820 8/1959 Australiam... ..56/l3.4

Primary Examiner-Russell R. Kinsey Attorney-Beveridge & De Grandi [57]ABSTRACT A lawn-mower with horizontally rotating knives has an ejectionaperture formed in a casing enclosing the rotary knives. Screening meansare arranged in the ejection aperture to prevent accidents. The knivesof the lawn-mower function in the manner of fan blades so as to causethe uncut grass to stand on end and to lift the cut-off grass blades toa level above the path of the knives. The knife unit also includesanother fan device which produces a flow of air directed towards theejection aperture and carrying the cut-off grass outwards through thisaperture. Further, screening means are disposed above the ejectionaperture at a level with the path of motion of the knives, and theejection of the grass has to take place through a portion of theaperture that lies above the screened portion of the ejection aperture.

3 Claims, 1 Drawing Figure L'AwN-MowERs wmr HORIZONTALLY ROTATING KNIVESThis invention relates to an improvement in such lawn-mowers withhorizontally rotating knives as have a casing enclosing the rotaryknives and formed with an ejection aperture, a tangentially arrangeddischarge portion and screening means serving as a protective deviceagainst accidental contact and as a guard against the ejection of hardsolid objects.

For safety reasons, conventional lawn-mowers of this type are providedwith a casing which encloses the rotating knives and is intendedto'prevent the operator from coming in accidental contact with and beinginjured by the knives and the ejection of stones and other solid objectswhich the knives encounter as thelawnmower is propelled-over the lawn.The casing which is closely spaced from the ground entails, however,also the disadvantage that the cut-off grass remains beneath thecasing,thatparticularly-long 'andmoist grass will collect andjbe deposited in.tufts giving the lawn an unpleasant appearance,:and moreover, the grassmay be compacted in the casing so that rotation of the knifes isprevented. In countries having less severe safety requirementslawn-mowers have been developed for ejection of the grass throughanaperture in the casing.

The present invention has for its object to provide an arrangement whichhas the undeniable advantages that are associated with an ejectionaperture for the cut grass and nevertheless satisfies very high safetyrequirements.

In thearrangement according to the present invention it is not only thedesign of the screening means and the ejection aperture that is decisivefor the function but also the design of the knife assembly and thedetails immediately surrounding it.

The arrangement according to the present invention is substantiallycharacterized in that the knives which in conventional manner areadjustably mounted to a disk connected to a drive shaft, are set in anoblique position similar to fan blades so that upon rotation said kniveswill produce an upwardly directed flow of air which causes the grass tostand on end and which lifts the cut grass to a level above the path ofmovement of the knives, that the disk carrying the knives has fan bladesor like means which are adapted to produce, in the space above the planeof rotation in which the knives move, a flow of air directed towards theejection aperture which opens tangentially with respect to the path ofthe knives, that the ejection aperture at a level with the path ofmovement of the knives is screened by means of a bar or like means whichin the direction of said path extends over the greater part of theejection aperture, said bar merging beyond said part of the aperture ina portion projecting tangentially through the ejection aperture,transverse screening means being disposed at the outer end of saidtangentially projecting portion which is spaced from the mouth of theejection aperture, and that a protective device against accidentalcontact is so arranged, in the partof the ejection aperture which issituated above the. screening means positioned at a level with the pathof movement of the knives, as to extend preferably in the ejectingdirection.

' The heavy straight, horizontally rotating knife blades cerned have avery large living force. In the arrangement according to the presentinvention, the knife blades have been replaced by a disk which operatesas a fan'and carries two adjustable knives. The knives are placed inoblique position and upon rotation therefore produce an upwardlydirected air flow which causes the grass to stand on end and which liftsthe cut-off grass upwards. Due to the fan action which is simultaneouslyprovided by the disk a vigorous air flow is produced within the casingat a level above the plane in which the knives rotate. It should bementioned that the suction realized with the aidof the oblique knivesand the fan disk is not so large that heavy objects such as stones canof a conventional lawn-mower of the type herein conbe lifted up andejected. An advantage gained by the described design of the knifeassembly is that the risk of the mower being damaged, as a rule a bentmotor shaft, is highly reduced in that theknifes will move aside whenthey encounter solid objects.

I In all of the prior art lawn-mowers having an ejection aperture'thecut-off grass is thrown out'of the casing in a'path contained in'orclose to the plane of rotation in which the knifes move. This makes itimpossible in practice to separate stones and heavy solid objectseffectively. However, such effective separation is realized byth'econstruction suggested in accordance with the present invention, inwhich the cut-off grass before ejection is lifted up to a level abovethe plane of rotation of the knives, while stones and heavy objectseither will remain lying on the ground or, if encountered by the knife,will be thrown about within the casing. If a knife should encounter astone in such a way as to throw it towards the ejection aperture thestone will be caught by the screen which is at a level with the plane ofrotation of the knives or by the transverse screening means spaced fromthe mouth of the ejection aperture.

. The ejection aperture proper which is at a level above the plane ofrotation of the knives is altogether free from details preventing thegrass to pass through said aperture. To prevent that the operators handsor feet might contact the knifes, inwardly tapering screens are providedin said aperture and so placed that there is no risk whatsoever of grasscollecting thereon.

One embodiment of the invention will be more fully described hereinbelowwith reference to theaccompanying drawing which in a perspective viewshows a partially cut open portion of a lawn-mower according to theinvention.

In the drawing, less relevant details such as wheels,

I drive motor and handles are not shown. The casing carried by thewheels is designated 1 and encloses the knife assembly which isgenerally designated 3 and is supported by the motor shaft 2. The knifeassembly includes a circular disk 4 at the periphery of which two knives6are mounted. The knives are in a known manner adjustably arranged onpins 5. In the embodiment illustrated the knives are somewhat obliquelypositioned similar to propeller blades and consist of relatively thinmetal profile members. The disk 4 has such a diameter that a space willbe left for the knifes between the preferably bent up edge 7 of the disk4 and the substantially vertical wall 8 of the casing l. A number of fanblade means 9 are disposed on the upwardly facing side of the disk 4. Adischarge portion 10 which is open downwardly extends tangentially tothe casing 1. That side 11 of said discharge portion which extendstransversely to the wall of the casing may be extended inwardly with theaid of a vane 12. The inner slightly curved end 12' of the vane 12should extend tangentially inwards to an axial plane passing through theperiphery of the rotary disk 4. The vane 12 has a vertical dimensionsuch that the. knifes 6 can pass beneath it. By giving the portion ofthe casing that surrounds the ejection aperture a suitable configurationin point of flow the vane 12 may, however, be dispensed with.

The provision of the blade means 9 on the disk 4 in combination with theoblique or inclined knifes 6 and the tangential discharge portion andpossibly the vane I2 will produce upon rotation of the disk and theknives an upwardly directed suction which tends to make the grass bladesstand on end and lift the cut-off grass blades, and also a vigorous airmovement which will throw the cut-off grass out of the casing.

One might think it possible to provide the discharge portion 10 with anoptional type of grid to prevent the ejection of heavy objects, saidgrid also serving as a protective device against accidental contact.However, experience has shown that conventional grids and like means arenot useful as they are very rapidly clogged by cut-off grass blades.This most probably is due to the different velocities of the grassblades depending upon what part of the discharge portion 10 they areejected from. The blades ejected close to the periphery of the casingand along a tangent have the highest velocity and run a relatively smallrisk of getting stuck and collecting, whereas the blades ejected alongthe opposite edge of the ejection aperture have a lower velocity andtherefore easily get stuck. In the first part of the opening the risk ofclogging is thus smaller. In the lawnmower of the present invention thisproblem has been solved by providing that part of the ejection aperturewhere the velocity is greater with a transverse bar 13 which is anextension of the lower marginal portion of the wall 8 of the casing,runs at a level with the rotary path of the knives and is adapted toprevent heavy solid objects to be thrown straight outwards by theknives, and also with contact protection guard means arranged outsidesaid bar 13 and having the form of two inwardly tapering metal plates 14which are carried by a U bar 15 secured to the outwardly projectingdischarge portion 10. Neither the bar 13 nor the U bar 15 having themetal plates 14, however, traverses the entire opening in the dischargeportion 10. Instead, the transverse bar 13 is bent abruptly outwardlyshort of the opposite wall and, as will appear from the drawing,connected with the U bar 15 so that a free space 16 remains adjacentthat edge of the opening where the velocity is lower. In the free space16 which contains no structure that would prevent the ejection of thegrass and that would be capable to catch it, no collection of grass cantake place. The risk that the ejection aperture will be clogged is thuseliminated. To prevent the ejection of heavy solid objects through thespace 16 a bent end portion 17 of the bar 13 extends perpendicularthereto some distance from the mouth of the discharge portion across theassumed path of a heavy object ejected through said free space 16. Theend or screening portion 17 is spaced such a distance from the mouththat the collection of grass thereon is of no significance for thefunction, but lies sufficiently close to catch or decelerate themovement of, ejected stones and like solid objects. Besides, the endportion 17 will form together with the metal plates 14 an efficientprotective device against accidental contact inasmuch as the freedistances between said parts are too small to allow for instance theoperators hand to penetrate past them into the working range of theknives.

The invention is not limited to the embodiment described above andillustrated in the drawing but can be modified in several ways withinthe scope of the ap pended claims.

What I claim and desire to secure by Letters Patent 1. A lawn-mower withhorizontally rotating knives of the type having a casing enclosing therotary knives and formed with an ejection aperture, a tangentiallyarranged discharge portion and screening means serving as a protectivedevice against accidental contact and as a guard against the ejection ofhard solid objects, wherein the knives which in conventional manner areadjustably mounted to a disk connected to a drive shaft, are set in anoblique position similar to fan blades so that upon rotation said kniveswill produce an upwardly directed flow of air which causes the grass tostand on end and which lifts the cut grass to a level above the path ofmovement of the knives, the disk carrying the knives has fan blades orlike means which are adapted to produce, in the space above the plane ofrotation in which the knives move, a flow of air directed towards theejection aperture which opens tangentially with respect to the path ofthe knives, the ejection aperture at the level of the path of movementof the knives is screened by means of a bar or like means secured tosaid casing which in the direction of said path extends over the greaterpart of the ejection aperture, said bar merging beyond said part of theaperture in a portion projecting tangentially through the ejectionaperture, transverse screening means being disposed at the outer end ofsaid tangentially projecting portion which is spaced from the mouth ofthe discharge portion, and a protective device supported on saiddischarge portion to prevent accidental contact with said rotatingknives is so arranged, in the part of the ejection aperture which issituated above the screening means positioned at a level with the pathof movement of the knives, as to extend preferably in the ejectingdirection.

2. A lawn-mower as defined in claim I, wherein the protective devicearranged in the ejection aperture is at least one inwardly taperingmetal plate extending in the direction of ejection and so arranged thatits one free edge is spaced from the opposite boundary wall of theejection aperture.

3. A lawn-mower as defined in claim 1, wherein the ejection aperture isdefined by said discharge portion portion of the casing which portionlike the casing proper is entirely open downwards.

1. A lawn-mower with horizontally rotating knives of the type having acasing enclosing the rotary knives and formed with an ejection aperture,a tangentially arranged discharge portion and screening means serving asa protective device against accidental contact and as a guard againstthe ejection of hard solid objects, wherein the knives which inconventional manner are adjustably mounted to a disk connected to adrive shaft, are set in an oblique position similar to fan blades sothat upon rotation said knives will produce an upwardly directed flow ofair which causes the grass to stand on end and which lifts the cut grassto a level above the path of movement of the knives, the disk carryingthe knives has fan blades or like means which are adapted to produce, inthe space above the plane of rotation in which the knives move, a flowof air directed towards the ejection aperture which opens tangentiallywith respect to the path of the knives, the ejection aperture at thelevel of the path of movement of the knives is screened by means of abar or like means secured to said casing which in the direction of saidpath extends over the greater part of the ejection aperture, said barmerging beyond said part of the aperture in a portion projectingtangentially through the ejection aperture, transverse screening meansbeing disposed at the outer end of said tangentially projecting portionwhich is spaced from the mouth of the discharge portion, and aprotective device supported on said discharge portion to preventaccidental contact with said rotating knives is so arranged, in the partof the ejection aperture which is situated above the screening meanspositioned at a level with the path of movement of the knives, as toextend preferably in the ejecting direction.
 2. A lawn-mower as definedin claim 1, wherein the protective device arranged in the ejectionaperture is at least one inwardly tapering metal plate extending in thedirection of ejection and so arranged that its one free edge is spacedfrom the opposite boundary wall of the ejection aperture.
 3. Alawn-mower as defined in claim 1, wherein the ejection aperture isdefined by said discharge portion portion of the casing which portionlike the casing proper is entirely open downwards.